For women under the age of 35, the chance of live birth success per single IVF cycle is on the order between 40 and 50 percent, based on national reporting of all fertility clinics in the US. The likelihood of pregnancy begins to decline every year after age 35. At 40 years old, the chance of live birth pregnancy per cycle is somewhere around 25 percent. At 42 years of age, that percentage approaches 15 percent. IVF is infrequently performed using a woman's own eggs at age 43, because success rates are around 10 percent. After age 43, IVF is not routinely performed using woman's own eggs as the chance of success diminishes to less than 10 percent per cycle. It is important to note that patients choosing to attempt to undertake IVF at 43 or older are select, often having a higher ovarian reserve relative to their age, and may not be representative of the general population.
Is there a surge in fertility in the years immediately prior to menopause? It is possible that there may be a slight relative increase as the body naturally stimulates the ovaries more aggressively. This phenomenon, however, has not been rigorously examined and confirmed. In the big picture, however, it is clear that the chance of a successful spontaneous pregnancy in women in her late 40s is very low - not zero - but low.
Of course, if you do not wish to become pregnant, be sure to continue to use a reliable birth control method through the entire perimenopausal period. Check with your doctor about when it might be safe to discontinue all birth control.